The present invention relates to a safety switch which is mounted on a wall surface of the doorway of a room for installing an industrial machine or the like, and which discontinues power supply to the industrial machine or the like when the door at the doorway is opened.
In a room or factory which accommodates an industrial machine, or in a danger zone around an industrial machine itself, it is required to install a system for locking the drive of the machine. The locking system operates when the door at the doorway for the room or danger zone is not closed completely, in order to prevent accidents in which an operator may get caught in the machine and injured.
With regard to a common locking system, a limit switch is disposed at the slidable portion of the door. The system provides power to the industrial machine inside the room, only when the limit switch detects the closure of the door.
Nevertheless, this locking system is not a perfect safety measure, because the machine inside the room can be turned operable, without closing the door, by manipulating the actuator of the limit switch.
In this respect, the applicant of the present invention has already proposed a safety switch for preventing such wrong operations (Japanese Patent Laid-open Publication No. H6-76674 (JP-A-6-76674).
The proposed safety switch has an operation section and a switch section, and comprises a switch body which includes a key insertion hole formed in the casing of the operation section (see FIG. 1) and an actuator composed of a base and an operation key provided therewith. The switch body is mounted on the wall surface around the doorway of the room, whereas the actuator is secured on the door (sliding or revolving door) at the doorway. On closure of the door, the operation key of the actuator enters the operation section through the key insertion hole in the switch body, causing the contact block housed in the switch section to switch over its moving contact. This switch-over action directs the circuit connection to the main circuit (power supply circuit for the industrial machine) and sets the machine in the room ready for operation.
In another use, the safety switch is disposed at a connection point with a mobile device which is connected to a teaching device or similar device body. When the mobile device is properly connected to the device body, the operation key of the actuator enters the switch body of the safety switch to set the device body to an operable state.
When the actuator for these safety switches is mounted on the door, the operation key is oriented horizontally or vertically, depending on the conditions of use (e.g. installation posture of the switch body).
However, in many of the conventional actuators, the operation key is fixedly held on the base with no freedom in movement. As illustrated in FIG. 29, if the actuator is used for a revolving door 10 with a small radius of revolution, the tip of an operation key 502 may interfere with a switch body 100 when the revolving door 10 closes. Because of this problem, a fixed actuator is not applicable to the revolving door 10 having a small revolution radius.
In order to solve this problem, another actuator (an operation key device for a safety switch) is disclosed in Japanese Patent Laid-open Publication No. H11-213820 (JP-A-11-213820), wherein the operation key is mounted on the base in such a manner as to be capable of swinging in orthogonal directions (horizontal and vertical directions). According to this actuator, however, the operation key is constantly swingable in two directions (horizontal and vertical directions), and held in a tilted posture both horizontally and vertically. Under these conditions, it is difficult to position this actuator relative to the switch body.
Made in view of such circumstances, the present invention intends to provide an actuator in which the operation key can move relative to the base, whereby the actuator becomes applicable to a revolving door with a small revolution radius and the like, and in which the movable direction of the operation key can be selectively changed over into either of the horizontal direction or the vertical direction.
In order to achieve the above object, the actuator of the present invention comprises an operation key to be inserted into a key insertion hole formed in the safety switch, and a base, characterized in that the operation key is held on the base and capable of freely swinging in two orthogonal directions, and also characterized in comprising means for selectively restricting the swinging movement of the operation key to either of the two directions.
The actuator of the present invention gives the operation key a freedom of being swingable in two directions (horizontal and vertical directions). Even if the operation key may interfere with the switch body on entry into the key insertion hole in the switch body, the operation key can swing to avoid such interference. Therefore, this actuator can be used, for example, for a revolving door with a small radius of revolution. Besides, the swinging direction of the operation key can be selectively changed over into either the horizontal direction or the vertical direction, so that the operation key is allowed to swing only in a direction in which the freedom is required. As a result, the safety switch can be installed without any difficulty in positioning the actuator relative to the switch body.
The actuator of the present invention may be provided with two engagement spaces which are formed in the base and a guide stopper which is configured to fit into each of the engagement spaces. By fitting the guide stopper selectively into either of the two engagement spaces, it is possible to restrict the swinging direction of the operation key to one direction.
The actuator of the present invention may comprise an adjustment mechanism for independently adjusting a swinging range of the operation key in each swinging direction. Thereby, the swinging range of the operation key can be easily set to a suitable range, depending on the conditions of use (e.g. revolution radius of a revolving door).
If the actuator of the present invention comprises an elastic member for biasing the operation key in each swinging direction, the operation key can be held at a certain position under an elastic force. In this case, the operation key may be biased in each swinging direction by a torsion force and a compression force both generated by a helical coil spring, so that the number of parts can be reduced (thus, the cost is reduced).